Tantalum base alloys



United States Patent Oflice 3,183,085 Patented May 11, 1965 3,183,085 TANTALUM BASE ALLOYS Leonard L. France, Mount Lebanon, Allen I. Lewis, deceased, late of Forest Hills, by Bernard J. Ambrose, administrator, Monroeville, Robert L. Ammon, Pleasant Hills, and Lee S. Richardson, Monroeville, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed Sept. 15, 1961, Ser. No. 138,530 Claims. (Cl. 75-174) The present invention relates to tantalum base alloys suitable for use where high strength and ductility at either subzero or elevated temperatures is required.

Fabricable alloys possessing strength and ductility at extremely high and extremely low temperatures have many industrial and military applications, and it is generally recognized that future developments in many fields are closely tied to the availability of new and improved alloys possessing these properties. For example, the development of improved rocket nozzles and blades for gas turbines is dependent upon the availability of such alloys.

In accordance with this invention, it has been found that workable alloys possessing unusually high strength and ductility at temperatures above 2000 F. and at temperatures as low as 320 F. can be produced by alloying tantalum with one or more of the metals tungsten, zirconium, molybdenum, hafnium, and vanadium, and, if desired, columbium, rhenium or titanium may be added in specified proportions to such alloys.

The object of the invention is to provide a readily workable cast member comprising at least two metals selected from the group consisting of tungsten, zirconium, molybdenum, hafnium and vanadium, with or without rhenium, columbium and titanium, the balance, over 50% by weight being tantalum, with small amounts of incidental impurities.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

In accordance with the present invention wrought members have been produced from a cast member comprising a multi-component tantalum base alloy comprising at least two metals selected from the group consisting of tungsten, zirconium, molybdenum, hafnium and vanadium and the balance being tantalum. The total amount of at least two of the added metals is at least 1% each and no added metal is to exceed 8% by weight of the alloy. Also, minor additions of the order of up to 2% of one or more of the metals columbium, rhenium and titanium may be made. The total amount of all the added metals is at least 2% and does not exceed 16% by weight of the alloy. The alloy contains at least one of the other beforementioned metals, excluding rhenium, when tungsten and hafnium are present. The alloys are characterized by high mechanical strength and ductility at elevated and subzero temperatures, and the ability to be easily wrought to shape by hot or warm working, or in certain alloy compositions, by cold working.

The alloy may be melted by one of several procedures which will insure homogeneity and a minimum of contamination. For example, unalloyed, high purity tantalum together with the proper amounts of the selected alloying components can be fed into a conventional non-consumable arc melting furnace containing an inert atmosphere, such as argon, or a vacuum. The resulting ingot should be remelted several times, preferably by consumable arc melting it, to achieve homogeneity, then it may be hot worked to the desired shape. The alloy may also be prepared by pressing together powders of tantalum and selected alloying components and consumably arc melting the same. Levitation melting of a ball or rod of the alloy, using induction heating, or electron beam melting are also satisfactory.

Referring to Table I there is set forth examples of the various compositions of alloys of the invention and the degree of workability in terms of percent reduction in area. It may be concluded therefrom that the alloys with the smallest amount of alloying components are more workable than those having higher amounts. In alloys having a total amount of 16% by weight of alloying components there appeared edge cracks after working an acceptable degree. However, in alloys containing above a total of 16% by weight of alloying components the edge cracks became too severe after working to render the final member useful.

Table I workability Percent Re- Composition (Weight percent) duction (one Results hammer blow at 1,200 C.)

97Ta 2W 1Zr 65 No cracks. 96Ta 2W 2Zr 57 Do. 92la 4W 4Zr 52 Edge cracks. 84Ta 8W 8Zr- 65 Do. 98'Ia 1M0 lHl 59 No cracks. 96Ia 2M0 21H 58 Do. 92Ta 4M0 4Hf 46 Slight edge cracks. 84Ta 8M0 8IIf. 52 Edge cracks. 98Ta 1M0 1Zr.-. 64 N0 cracks. 96Ta 2M0 2Zr 57 Slight edge cracks. 92Ta 4M0 4Zr 56 Edge cracks. 97'1a 2W 1V. 61 No cracks. 96'Ia 2W 2V 58 Do. 921a 4W 4V 48 Slight edge cracks. 84'Ia 8W 8V- 45 Edge cracks. 98Ta 1M0 1V.-. 66 No cracks.

92la 4M0 4V 46 Edge cracks. 84Ta 8M0 8V 38 Do.

Referring to Table H, there is shown forthe various compositions of the invention the results of hardness tests performed on the alloys in the as-cast condition and after homogenization at 2000 C. Homogenization generally softened the metal structure by elimination of coring and residual stresses, but in some cases raised the hardness level. This was most likely due to an increase in solid solution components upon equilibrium annealing or to an aging reaction producing a fine, invisible precipitate at the annealing temperature.

Table II Hardness (DPH) Com osition Wei ht percent) p g As cast After 2,000

0. Home.

98Ta 1 Mo 1Zr 187 187 96Ta 2M0 2Zr- 286 331 92'la 4M0 4Zr. 313 351 98Ta 1M0 1Hf 166 152 96Ta 2M0 2Hf 212 238 92Ia 4M0 4Hf 281 313 84Ta 8M0 8Ht 383 410 97Ta 2W 1Zr 176 96Ta 2W 2Zr. 193 94Ta 2W 4Zr 228 270 92Ta 4W 4Zr 262 301 88'Ia. 8W 4Zl 316 344 97Ia 2W 1V 171 166 96Ta 2W 2V- 197 183 94Ta 4W 4V. 280 268 84Ta 8W 8V 388 375 The following example is illustrative of the present invention.

An alloy of the following composition was prepared by consumable arc melting: 92% tantalum, 4% molybdenum, and 4% hafnium. The alloy could be hot worked. Samples were cut from the resulting ingot and were tested at temperatures ranging from 320 F. to 2700 F. for ultimate tensile strength, yield strength, percent elongation and percent reduction in area. sults were obtained:

The following re- It may be concluded from these tests that the alloy has a relatively high strength and ducility at both subzero and at elevated temperatures.

It will be understood that the above description is only exemplary and not in limitation of the invention.

What is claimed is:

1. A readily workable member comprising a tantalum base alloy consisting of by weight 1 to 8% tungsten, 1 to 4% zirconium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

2. A readily workable member comprising a tantalum base alloy consisting essentially of by Weight 1 to 8% molybdenum, l to 8% hafnium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

3. A readily workable member comprising a tantalum base alloy consisting of by weight 1 to 8% molybdenum, l to 4% zirconium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

4. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 1 to 8% tungsten, 1 to 8% vanadium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

5. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 1 to 8% molybdenum, 1 to 8% vanadium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

6. A readily workable cast member comprising a tantalum base alloy consisting of by weight 8% tungsten, 4% zirconium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

7. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 8% molybdenum, 8% hafnium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

8. A readily workable member comprising a tantalum base alloy consisting of by weight 8% molybdenum, 4% zirconium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

9. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 8% tungsten, 8% vanadium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

10. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 8% molybdenum, 8% vanadium and the balance tantalum with small amounts of incidental impurities, the member being characterized by relatively high strength at elevated temperatures and relatively good ductility at room and even lower temperatures.

References Cited by the Examiner UNITED STATES PATENTS 2,957,764 10/ Michael -174 3,022,163 2/62 Lottridge et al. 75-174 3,043,683 7/62 Hix 75-174 3,075,840 1/63 Donlevy 75-174 FOREIGN PATENTS 225,656 3/59 Australia.

OTHER REFERENCES Metallurgia, vol. 52, No. 248, June 1950 (The British Journal of Metals), pages 1-9 relied upon.

Niobium, Tantalum, Mo and W, A. G. Quarrell, Elsevier Publishing Co., New York, 1961, pages 113, 335-346. (Conference papers published and available by August 17, 1960).

Tantalum and Niobium, G. L. Miller, Academic Press Inc., publishers, New York, 1959, pages 544-546.

DAVID L. RECK, Primary Examiner.

RAY K. WINDHAM, WINSTON A. DOUGLAS,

Examiners. 

1. A READLY WORKABLE MEMBER COMPRISING A TANTALUM BASE ALLOY CONSISTING OF BY WEIGHT 1 TO 8% TUNGSTEN, 1 TO 4% ZIRCONIUM AND THE BALANCE TANTALUM WITH SMALL AMOUNTS OF INCIDENTAL IMPURITIES, THE MEMBER BEING CHARACTERIZED BY RELATIVELY HIGH STRENGTH AT ELEVATED TEMPERATURES AND RELATIVELY GOOD DUCTILITY AT ROOM AND EVEN LOWER TEMPERATURES. 